Truck mounted cranes have seen increasing popularity over the last several years. Such cranes are employed for a variety of uses. In the most familiar use, they are employed for loading or unloading the contents of the truck bed. An auxiliary use may include the handling or manipulation of some object in addition to the usual loading and unloading function. An example of the latter resides in servicing the tires of large wheeled vehicles as, for example, agricultural tractors, off the road vehicles, etc.
In any event, one highly desirable requisite of such cranes is that they be foldable to a compact storage and travel position. In short, when the crane is not being used and the vehicle is travelling from one point to another, the crane should occupy minimum space on the truck. Firstly, this will allow the load of the truck, in terms of space, to be maximized. Secondly, it will allow the truck to readily move between points without concern for obstructions along its route as, for example, low bridges, tunnels, low hanging vegetation or wires, etc.
As a consequence of these desires, a typical truck mounted crane is provided with an upright mast which most frequently will be pivoted to the bed of the truck near one end thereof for rotation about a vertical axis. The upper end of the mast will typically pivotally mount a boom assembly consisting of an inner boom and an outer boom pivoted thereto. In many cases, the outer boom will be made up of telescoping elements so that its length may be selectively varied as required.
For storage purposes, the outer boom will typically be retracted to its shortest length and folded under the inner boom. In some cases, the remote end of the outer boom may be caused to pass through a space in the mast or, alternatively, to one side of the mast such that in silhouette, a figure "4" configuration is assumed.
In many instances, this storage configuration is totally satisfactory for the purpose. However, it does have some limitations which may be critical in some cases.
For example, the vertical compactness of such a crane is limited by the height of the mast. The taller the mast, the less the vertical compactness.
When vertical compactness is to be achieved by shortening the mast, the elevational or vertical reach of the crane is accordingly reduced.
In some instances, the mast may be canted at an angle of 40-50.degree. to the vertical to thereby reduce its vertical height. Canting will typically be in the direction away from the boom with the result that both vertical and horizontal reach are sacrificed.
The present invention is directed to overcoming one or more of the above problems.